i think you under rate these aliens; in bigger scenarios, there is no limitation and basicly you could go for so big fleets (and resulting reward) that the speed up isn't interesting anymore... but why big players dont do that?
I think you are wrong here. Of course I understand how powerful aliens are, and I have to say it's an amazing option. And I want to use it soon, but I need some prepare first. But there are two things:
1. I think players do not understand that mechanic. For me, it took over a month to fully understand the mechanics. Many times I asked you directly how it works cause nobody knew it. Even 'dark angel' who is I think really old player here didn't know how exactly aliens work. I think that this is one thing, players maybe even tried to intercept aliens but they couldn't and they didn't know why cause it wasn't explained anywhere. I think that aliens FAQ should be updated a little bit about this informations how aliens rage attacks work.
2. It's really hard to do cause you need at least two players. I tried to do interceptions couple of times already with different players. The hardest part is to coordinate with each other. I want to do this today, but guy can only at weekend, then at weekend we do this, we spend half of a day for it, then before we can make new planet next to the second alien the weekend is over, guy or me got work to do, so we have to wait whole week to make it again, next weekend he can't cause he also has a live etc.
It's really hard to coordinate on that with that small amount of players that we have now.
So I agree, there is activity, and it's really strong activity, and potential profits are great. But player doesn't understand that, and they can't do this solo. I think that's why it's not so popular